1. Field of the Invention
This invention relates to a method for selective electroplating with an unsubmerged jet, and more particularly to masking improvements therefor.
2. Description of the Prior Art
The principles of electroplating with an unsubmerged jet and its concomitant advantages of selective electroplating and high speed are well known in the art, cf., for example, the publication entitled "High-Speed Selective Electroplating with Single Circular Jets", R. C. Alkire et al, Journal of the Electrochemical Society, Vol. 129, No. 11, November 1982, pages 2424-2432.
Briefly, in these systems, a jet of electroplating solution is discharged from a nozzle and impinges on the region of the workpiece to be plated. The jet is discharged unsubmerged, that is to say, the jet when emerging from the nozzle passes through a medium, e.g. air, that is extremely less viscous than that of the electroplating solution. Such jet systems are referred to in the art, and as used herein, as a free or unsubmerged jet system to distinguish them from other jet systems where the jet is discharged into a surrounding medium which is the same as the plating solution, the latter being known and referred to in the art as a submerged jet system. The free or unsubmerged jet thus provides an electric current path between the anode of the system, which is located upstream in the nozzle, and the external workpiece, which is the system's cathode. As a result, electrodeposition takes place on the workpiece at the impingement region and surrounding vicinity of the workpiece in a selective and high speed manner.
Moreover, as explained in the aforementioned publication, the customary case, particularly in commercial systems, is to direct the jet at the workpiece region where the plating is to take place without any masking. On the otherhand, in the case where masking is used in the prior art of which we are aware, these masks have been solids. However, in both of the aforementioned cases, i.e. the unmasked case and the solid mask case, there are certain attendant problems, disadvantages and/or deleterious effects associated with each case.
For example, in the unmasked case, extraneous electroplating solution resulting from such things as runoff of the electroplating solution or splashing of the solution from the impinging jet causes some of the plating material to be electrodeposited on parts of the workpiece not desired or required to be plated. As a result, in the prior art not only was the material plated to the region of interest but it also became plated to other regions which were not of interest. The plating on the regions, which were not of interest, is sometimes referred to herein as background plating. This background plating is often detrimental to the function or the aesthetics of the plated regions of interest of the workpiece such as, for example, in the fabrication of selectively plated high precision electrical components or of selectively plated ornamental objects such as costume jewelry or the like. Moreover, in the unmasked case, there was a concomitant wastage of the plating material as a result of it being plated to the unwanted, i.e. the not-of-interest, regions. The wastage thereby increased the cost of the process and the ultimate product and which can be quite substantial if the particular material being electrodeposited happens to also be a precious metal such as gold or the like. Even in those situations where it is desirable and practical to reclaim the plated material from the unwanted regions, it nevertheless adds to the complexity and cost of the overall process for fabricating the resultant work product.
Likewise, in the case of the solid mask, it too also adds to the cost and complexity of the electroplating process per se and the overall fabrication process in general. In the solid mask case, the additional costs and complexity are associated with the making, applying and/or subsequent stripping of the mask. Moreover, the solid mask is not always easily or able to be applied and/or removed and this is particularly true where there are hard to reach or inaccessible regions of the workpiece that are desired to be masked.